Oksana Grigorieva has told law enforcement authorities probing Mel Gibson for domestic abuse that she once witnessed the Oscar-winning actor/director hit his youngest son Tommy, RadarOnline.com has exclusively learned.

The Russian musician, 40, is also claiming that Mel admitted throwing a television at his ex-wife, Robyn, at one stage during their 29-year marriage.

RadarOnline.com has confirmed the explosive allegations of more violence are part of three separate law enforcement investigations underway into the star, after Oksana claimed Mel punched her twice, attempted to strangle her and then threatened to kill her and their nine-month-old daughter Lucia.

The claims have also been made to Russian newspaper, Komsomolskaya Pravda, from a source purported to be a “family friend” of the singer/pianist

RadarOnline.com learned that Oksana alleged the Lethal Weapon star hit Tommy in the head, while at a hockey game at Staples Centre, two-and-a-half-years ago.

The new claims add yet another twist in the bitter battle between the Mel and Oksanar and could result in Mel’s own children being forced to be called as potential witnesses against their father.

As we revealed, Oksana told authorities investigating Mel for domestic violence that another of the actor’s sons witnessed his father’s violence in a December 2009 incident, when he allegedly picked up a chair and slammed it through a glass door.

Oksana’s mother, Ludmila, and son, Sascha, 12, were also in Mel’s mansion when the incident took place.

One of Mel’s sons rushed into the room after the glass was shattered and tried to calm Mel, Oksana told authorities.